Grassland and land management in the Southwest

Alice L. Chung-MacCoubrey 1

Abstract.—Of the research that has been conducted in the Southwest- ern states, few studies have addressed species inhabiting grasslands and the potential effects of management activities on these populations. Up to 17 bat species may be found regularly or occasionally in Southwestern grasslands or short-grass prairie. Main habitat requirements of grassland-dwelling bats are suitable roosts, water, and food. Livestock grazing, fire suppression, mining, bridge construction, agriculture, and urbanization affect the quality, quantity, and distribution of these resources. Effects of activities may not always be negative. Management activities and the natural distribution of roost, water, and food resources ultimately influence the distribution, abundance, and species composition of bats in grasslands. Research is needed to further identify resource requirements and use by grassland-dwelling bats and to confirm specific effects of human activities on local populations.

INTRODUCTION between insects and plants, , and other entities, bats are integral to the function and Among the many objectives of ecosystem man- integrity of many ecosystems. The diverse habitats agement are the preservation of viable populations of New Mexico and Arizona support up to 28 of species native to the ecosystem, and the protec- species of bats (Findley et al. 1975; Hoffmeister tion and maintenance of ecological processes and 1986), many of which are found regularly or species interrelationships (Grumbine 1994; Thomas occasionally in grasslands. 1994). Nonetheless, much of the information This paper reviews the basic habitat require- needed to achieve these objectives is unknown. In ments of bats, bat species that use grassland habi- this paper, Southwestern grasslands refers to the tats, and the potential effects of historic and cur- plains-mesa and desert grasslands of New Mexico rent management practices on resources important and Arizona (Lowe and Brown 1973; Dick-Peddie to grassland-dwelling bats. The information in this 1993; McClaran 1995). To balance human use and review will provide land managers with a better conservation of these arid grasslands, knowledge understanding of bats and the potential influence of of the life history, habitat requirements, inter- human activities on bats in Southwestern grasslands. relationships of animals, and the effects of man- agement practices on different species is necessary. Bats, the only true volant , are a most HABITAT REQUIREMENTS OF unique, but often overlooked, group of animals. SOUTHWESTERN BATS Bats feed on nocturnal flying and terrestrial in- sects, and likely play a role in regulating insect Appropriate roosts, available surface water, and populations (Ross 1967) and insect-related ecologi- food are essential components of suitable bat cal processes. By helping to maintain a balance of habitat in the Southwest. Because of their small relationships within the insect community, and size, the energetic demands of flight, a limited ability to store fat, and the seasonal abundance of 1 Research Wildlife Biologist, Rocky Mountain Forest and their prey, bats have an annual energy budget that Range Experiment Station, Albuquerque, NM 87106. is difficult to balance (McNab 1982). Energy expen-

54 ditures are regulated through roost selection (Kunz stock- tanks, perennial streams, drainage ditches, 1982; Hill and Smith 1984). Consequently, repro- or the closest river. Prior to livestock grazing, bats ductive success and overwinter survival of indi- may have relied on sparsely distributed springs, viduals and populations may largely depend on seeps, and permanent water sources. Historically, the availability of suitable roosts (Humphrey the geographic distribution of species not adapted 1975). For colonial bats, suitable maternity roosts for water conservation or for long distance flight provide a microclimate that facilitates gestation in may have been limited by water availability. pregnant females and rapid growth of the young However, construction of water holes and place- (Humphrey 1975). Appropriate winter hibernacula ment of stock tanks in Southwestern grasslands (hibernation sites) minimize the potential for over the last 100- 150 years have increased the disturbance and arousal and maximize efficient quantity and distribution of water available. Areas use of energy reserves. Therefore, overall distribu- originally devoid of water may have become viable tion and abundance of suitable roost sites (summer roosting and foraging habitat to other bat species and winter) may ultimately determine the distribu- (Geluso 1978). Because few records document bat tion and abundance of many bat species distributions prior to livestock grazing in the (Humphrey 1975). Local distribution and site use Southwest, it is impossible to confirm whether may also be influenced by factors unknown to or ranges of such species (e.g., fringed myotis, long- unstudied by the scientific community such as legged myotis, etc.) have expanded into grasslands threat by predators, distance to or availability of and deserts due to the increased number of water local hibernacula, and sensitivity to human distur- holes and stock tanks. bance. Food availability also determines bat species Surface water for drinking is another critical distribution and habitat use. Although insects component to bat habitat in the Southwest. Due to appear to be so abundant as to preclude competi- their high protein diet, insectivorous bats require tion between bat species (Ross 1967; Humphrey water to excrete toxic nitrogenous waste products 1975), dietary partitioning among insectivorous bat (McNab 1982). In addition, desiccating environ- species may be evident from their wide range of ments cause high rates of evaporative water loss sizes, flight styles, echolocating abilities, and the through wing membranes and respiratory ex- partitioning of vertical and horizontal space dur- change (McNab 1982). California myotis (Myotis ing foraging (Black 1974). Nonetheless, our under- californicus), western pipistrelle (Pipistrellus standing of the food habits and dietary preferences hesperus), pallid bat (Antrozous pallidus), and the of insectivorous bats is extremely limited. Nonde- Mexican free-tailed bat (Tadarida brasillensis) have structive methods of studying diet, the difficulty high urine-concentrating abilities or renal struc- with which arthropod remains are identified and tures that suggest they produce highly concen- quantified in feces, and the lack of methods to trated urine (Geluso 1978). As a result, these arid- effectively sample species composition and sea- dwelling bats are more efficient at conserving sonal abundance of arthropods have limited the water. More mesic species with distributions that number of dietary studies conducted. The insect include or extend into grasslands and deserts orders Lepidoptera (moths) and Coleoptera (beetles) (long-legged myotis [Myotis volans], fringed myotis are numerous and diverse and probably represent [M. thysanodes], little brown myotis [M. lucifugus], a universally available food source for most bat Yuma myotis [M. yumanensis], Townsend’s big- species (Ross 1967). In New Mexico, California eared bat [Piecotus townsendii]) have low urine- myotis, western pipistrelles, and long-legged concentrating abilities (Geluso 1978) and probably myotis are classified as moth strategists, and pallid select habitat with a greater emphasis on water bats, long-eared myotis (M. evotis), and fringed availability. myotis are classified as beetle strategists (Black Based on physiological adaptations to water 1974). However, all of these species consume a conservation or lack thereof, bats must find roosts diversity of arthropods in addition to moths and and foraging areas that have water within an beetles, including Orthoptera (grasshoppers), economical flight distance. Bats foraging in grass- Hymenoptera (bees/wasps), Diptera (flies), lands and desert scrub probably seek water at Homoptera (leafhoppers), Hemiptera (true bugs),

55 and Isoptera (termites) (Ross 1967; Black 1974; BATS OF SOUTHWESTERN GRASSLANDS Whitaker et al. 1981). Diet composition also likely reflects seasonal peaks of different arthropod In the eastern half of New Mexico, plains-mesa species (Black 1974) and probably varies with grasslands grade into and, depending on the habitat type. Consequently, differences in insect classification scheme, are considered part of the fauna between two habitat types may cause grass- short-grass prairies of the Great Plains (Wright and land-dwelling bats to have different diets than Bailey 1980; Dick-Peddie 1993). Because these individuals of the same species from adjacent grassland types are similar and animals do not habitats. Further studies of insect availability and recognize artificial boundaries, bats found in dietary preferences and requirements of bats are Southwestern grasslands (New Mexico and Ari- needed to interpret the effects of human activities zona) and short-grass prairie (northern Texas, on bat populations. western Oklahoma, southwestern Kansas, and Table 1. Federal status and types of summer roosts used by bats in Southwestern grasslands and short-grass prairies.

Species USFWS status Types of summer roosts

Species more commonly associated with grasslands Small-footed myotis Species of concern Cracks and crevices of cliffs and rocks, abandoned buildings and barns, (Myotis ciliolabrum) under rock slabs and loose bark; possibly in caves and mine tunnels. California myotis Cliffs, hillsides, rock outcrops, mine shafts, barns, houses, under tree bark (M. californicus) and sign boards, amongst desert shrubs, and on the ground. Cave myotis Species of concern Primarily caves and tunnels; occasionally buildings, bridges, and under rocks. (M. velifer) Pallid bat Rocky outcrops, crevices, caves, mine tunnels, buildings, and under rocks. (Antrozous pallidus) Western pipistrelle Canyon walls, cliffs, and other rock crevices; under rocks, in burrows and (Pipistrellus hesperus) buildings. Mexican free-tailed bat Caves, mines, bridges; occasionally in buildings. (Tadarida brasiliensis) Species found in grasslands given appropriate habitat Buildings, hollow trees, natural crevices, mines. (M. lucifugus) Yuma myotis Species of concern Crevices, mines, caves, buildings. (M. yumanensis) Fringed myotis Species of concern Caves, mine tunnels, rock crevices, old buildings. (M. thysanodes) Long-legged myotis Species of concern Abandoned buildings, cracks in ground, cliff face and other crevices, (M. volans) under loosebark. Long-eared myotis Species of concern Tree hollows, loose bark, folds of wood/bark, rock crevices, abandoned (M. evotis) buildings, mines. Hoary bat Foliage of trees and shrubs. (Lasiurus cinereus) Silver-haired bat Hollow trees, woodpecker holes, under loose bark, and in buildings. (Lasionycteris noctivagans) Eastern red bat Foliage of trees and shrubs, clumps of Spanish moss. (Lasiurus borealis) Big brown bat Hollow trees, rock crevices, mine tunnels, caves, buildings; occasionally in (Eptesicus fuscus) cliff swallow nests. Townsend’s big-eared bat Species of concern Caves, mine tunnels, and abandoned buildings. (Plecotus townsendii) Spotted bat Species of concern Cracks and crevices in rocky cliffs or under loose rocks. (Euderma maculatum) Big free-tailed bat Species of concern Crevices in rocky cliffs, buildings. (Nyctinomops macrotis)

56 eastern Colorado) have been reviewed together. Southwestern Biology were collected from grass- Information in this paper has been drawn from lands or riparian habitats within grasslands state fauna texts (Findley et al. 1975; Bee (Findley et al. 1975). et al. 1981; Hoffmeister 1986; Schmidly 1991; Occurring from deserts to ponderosa pine Armstrong et al. 1994), related literature, and per- forests, California myotis is one of the more com- sonal observation. The United States Fish and Wild- mon species captured in grasslands (O’Farrell and life Service classification for the species and types Bradley 1970; Findley et al. 1975). Aside from of structures used as summer roosts are in table 1. nursery colonies, which may roost communally in The structure and complexity of vegetation and one location most of the summer, small groups and the physical environment are factors that deter- individual California myotis show little roost site mine the use of habitats by vertebrates (Humphrey fidelity. California myotis appear to have flexible 1975; Grant et al. 1982; Parmenter et al. 1994). The roosting habits and a ubiquitous supply of roosts; apparent lack of vertical structure in grasslands thus, they have little loyalty to any one site seemingly indicates a lack of roosts and roost (Krutzsch 1954; Hirschfield et al. 1977). diversity for bats. However, size and Western pipistrelles occur from desert scrub to mobility determines the scale at which habitat ponderosa pine forests, but are most commonly selection occurs. A high degree of mobility allows found near rocky cliffs and canyons in desert and bats to select habitats at the landscape level and to grassland environments (Findley et al. 1975; utilize patches of resources that are separated by Hoffmeister 1986). Although pipistrelles typically significant distances (Kunz 1982; Schmidly 1991). roost in canyon walls, rocky cliffs and outcrops, Their small size allows them to exploit practically and under rocks on the ground, they are also any sheltered site. Most grasslands encompass found dayroosting in mine shafts and buildings. patches of other habitat types (Parmenter et al. A common inhabitant of Southwestern deserts 1994) and thus provide a surprising diversity and and grasslands, the pallid bat is frequently found abundance of roost sites. Bat roosts within grass- around rock outcrops and water, but also in areas lands may include crevices in and under stones devoid of these features (O’Farrell and Bradley and rocks, excavated or natural holes in the 1970; Findley et al. 1975). Roosting in rock crevices ground, and the foliage of scattered shrubs and and man-made structures, males and female pallid trees. Interspersed within grasslands, patches of bats are gregarious with members of the same sex other habitat types such as rock escarpments, talus (Hermanson and O’Shea 1983). slopes, cliff faces, lava flows and tubes, caves, open Another desert and grassland bat, the cave mines, and bridges, provide a host of different myotis, is found in the grasslands of Texas, west- roost environments for grassland bats. In addition, ern Oklahoma, southcentral to southwest Kansas, bats may roost within the foliage, bark, and cavi- and southern New Mexico and Arizona (Kunz ties of riparian vegetation along arroyos, tributar- 1974; Findley et al. 1975; Bee et al. 1981; Caire et al. ies, and rivers that pass through grasslands. 1984; Hoffmeister 1986; Schmidly 1991). The cave Bat species commonly captured within South- myotis roosts colonially in caves and mines and is western grasslands and short-grass prairies are the often found foraging over watercourses in deserts more xeric-adapted bats, including small-footed and grasslands (Hayward 1970; Findley et al. 1975; myotis (Myotis ciliolabrum), California myotis, Fitch et al. 1981). western pipistrelle, pallid bat, cave myotis (M. Mexican free-tailed bats are common in pinyon- velifer), and the Mexican free-tailed bat. Small- juniper woodlands, desert grasslands, and desert. footed myotis are grassland-adapted bats that This species typically roosts colonially in caves, often roost in rocky outcrops found throughout rock crevices, under bridges, or in buildings short-grass prairies (Bogan In press). This species (Findley et al. 1975; Wilkins 1989). Adapted for fast is documented from chalk bluffs and canyons in and long distance flight, these bats are known to western Kansas and the grasslands of eastern travel up to 50 miles to forage in a single night Colorado (Robbins et al. 1977, Armstrong et al. (Hoffmeister 1986). 1994). Twenty-four percent of the small-footed Other features within grasslands provide addi- myotis museum specimens in the Museum for tional types of roosting and foraging habitat and

57 allow many nonxeric-adapted bat species to oc- junipers, tree stumps, and small groups of rocks cupy grasslands. Trees along streams and rivers (pers. obs.). Thus long-eared myotis may be found provide roosts to hoary bats (Lasiurus cinereus), using these structures where available in grasslands. silver-haired bats (Lasionycteris noctivagans), and Information on habitat distribution and roost eastern red bats (Lasiurus borealis) (Findley et al. selection by different bat species comes from 1975; Hoffmeister 1986; Armstrong et al. 1994). netting records, museum specimens, and observa- Watercourses, trees, and man-made structures also tions. However, records are not complete through- provide foraging and roosting habitat for broadly out each species’ geographic range, not all habitat distributed species such as big brown bats types have been sampled equitably, and all sam- (Eptesicus fuscus), little brown bats (M. lucifugus), pling techniques are somewhat biased. Thus, and Yuma myotis (Jones 1965; Findley et al. 1975; sampling techniques used and areas and habitats Barclay and Cash 1985; Hoffmeister 1986; sampled should always be considered when Armstrong et al. 1994). Scattered caves, mines, evaluating the geographic presence or absence, buildings, and lava tubes found throughout grass- habitat associations, and habitat requirements of lands provide roosts for Townsend’s big-eared different bat species. Southwestern grasslands and bats and big free-tail bats (Nyctinomops macrotis) short-grass prairies probably have not been (Findley et al. 1975, Humphrey and Kunz 1976; sampled as extensively and thoroughly as other Kunz and Martin 1982; Caire et al. 1984; Genter habitat types. Additional studies (e.g., surveys, 1986; Hoffmeister 1986). A Townsend’s big-eared radiotelemetry, light tagging, etc.) in grassland bat and Yuma myotis captured over an isolated areas would contribute to a comprehensive under- desert spring in Nevada indicate that these species standing of which bat species use grasslands and may venture into desert areas practically devoid of which habitat components are important. water (O’Farrell and Bradley 1970). Rocky cliffs and canyons may provide summer roosts for spotted bats (Euderma maculatum) (Findley et al. EFFECTS OF CURRENT AND 1975; Schmidly 1991). Originally thought to occur HISTORIC MANAGEMENT PRACTICES primarily in mesic areas like ponderosa pine and mixed conifer, spotted bats have also been found The quantity, quality, and distribution of re- in xeric habitats of Utah (Geluso 1978; Storz 1995). sources available to bats in grassland environ- The ability of spotted bats to concentrate their ments have been altered by historic and current urine indicates that this species may have evolved management practices. Activities that have prob- in more arid environments such as deserts and ably had major influences on roost, water, and grasslands (Geluso 1978). foraging resources of bats in grassland areas Species with centers of distribution in other include grazing, fire suppression, mining, road habitat types that may occur peripherally in grass- and bridge construction, agriculture, and urbaniza- lands include the fringed myotis and long-legged tion. Human activities often change the structure, myotis. Although long-legged myotis and fringed composition, and distribution of vegetation and myotis typically occur in pinyon-juniper, oak other resources at a local or landscape level. Be- woodland and higher elevations, they have been cause of different resource requirements, some occasionally captured in grasslands and desert in wildlife species benefit from human-induced New Mexico and Arizona (O’Farrell and Bradley changes and some experience negative impacts. 1970; Findley et al. 1975; Hoffmeister 1986). A Grazing outside a cattle exclosure resulted in a maternity colony of fringed myotis near Isleta shift to bird and small mammal species that pre- Cave in New Mexico likely foraged in nearby ferred more xeric and open habitats. Inside the grasslands (Findley et al. 1975). In Texas, the long- exclosure, species preferring mesic and densely legged myotis is rare, but fringed myotis are vegetated habitats remained (Bock et al. 1984). present and seem to prefer grasslands at interme- Grassland fires adversely affect wildlife species diate elevations (Schmidly 1991). In pinyon-juniper that prefer dense litter and woody plant cover, but woodlands of New Mexico, long-eared myotis enhance habitat for species that prefer large- frequently nested in folded bark and wood of seeded herbaceous dicots (MacPherson 1995).

58 Little research has been conducted to determine ing, fire suppression, and agriculture are indirect, how human activities may change landscapes to complex in nature, and not readily apparent. Such benefit or adversely affect different bat species in effects are difficult to assess and remain unstudied. Southwestern grasslands. The effects of grazing, Abandoned underground and surface mines in fire suppression, urbanization, etc. can only be New Mexico have significantly increased the speculated based on the effects of these activities number of potential sites for day and night roosts, on known resource requirements of bats. maternity colonies, hibernacula, and migratory The distribution and availability of water to stopovers for bats. Twenty-nine of the 42 species in grassland bats have largely been influenced by the United States use abandoned mines to some livestock management practices and to some degree (Belwood and Waugh 1991). Twenty percent degree by urbanization. In addition to altering of mine features examined in New Mexico in one plant species composition and abundance in year showed enough bat use to warrant the gating riparian areas, livestock can also eliminate riparian of entrances instead of mine closure (Altenbach and areas through channel widening, channel aggrad- Milford 1991). A minimum of 1800 underground ing, or lowering of the water table (Saab et al. mines and 3400 surface mines exist on or near 1995). The impacts of cattle on Southwestern national forests in New Mexico alone (Shields et al. grasslands for over 100 years has likely led to the 1995). Mining has created an enormous supply of degradation or elimination of many native water potential roost sites to cave and rock-dwelling bat sources (seeps and springs). However, numerous species and those that have been displaced from steel and dirt stock tanks created throughout their traditional roosts. However, the closure of grasslands and other arid habitats have increased abandoned underground mines occupied by the quantity and distribution of water to bats. reproductive or hibernating bats has probably Thus, populations of native grassland and desert- been the demise of many hundreds or thousands adapted bat species may have actually benefited of bats. Bridges, houses, barns, and other man- from this grazing practice. In addition, less xeric- made structures found throughout grasslands have adapted bat species from adjacent pinyon-juniper, also increased the number and type of roosts oak woodland, and riparian habitats may have available to many bat species. However, many expanded their distributions into grassland areas modern structures are built to exclude bats, older that were previously unsuitable. However, indi- buildings are often bat-proofed by their owners, viduals of these species cannot rely on these man- and newer bridge designs may not be suitable for made water sources. Tank pumps are turned on occupation by bats (Keeley and Bloschock 1995). and off depending on the presence or absence of Human activities influence the food and roost cattle at particular sites, and the fill status of many resources available to bats indirectly by altering dirt stock tanks is dependent on seasonal precipita- the structure and composition of vegetation at tion. The growth of cities in or bordering on grass- local and landscape levels. Grazing and fire sup- lands has also affected the availability of water to pression interact to influence the number and grassland-using bats. Pools, ponds, irrigation and types of roosts available to bats and perhaps more drainage ditches, and other accumulations provide significantly, the species composition and abun- water to bats willing to colonize urban areas (e.g., dance of their prey base. General consensus exists big brown and little brown bats). that historic grazing and a subsequent reduction in The two other essential resources to bats, roosts fire frequency has led to a decrease in grasslands and food, are either directly or indirectly affected and an increase in desert shrubland (Branson 1985; by human activities. The direct influence of stock Dick-Peddie 1993; MacPherson 1995; Saab et al. tanks, mines, and man-made structures on bat 1995). By compacting soil, removing plant cover, roosting behavior, habitat use, and species distri- and indirectly reducing water infiltration, cattle bution is evident by their use of these structures. decrease vegetation density and alter plant com- This influence is somewhat quantifiable through munity structure and composition (Saab et al. capture, mine surveys, and examinations of 1995). The reduction of fine fuels to support the bridges, buildings, and other structures. However, spread of fire and fire suppression by humans are the effects of other human activities such as graz- probable causes for the decrease in fire frequency

59 in the past 130 years (Wright 1980; MacPherson activity patterns, seasonal peaks of abundance, 1995). Without fire to suppress the recruitment and etc.) are consistent, changes in insect species growth of woody plants and because of the collec- composition may not greatly affect bats that have tion of fertile, but loose interspace soils under flexible diet preferences. Bats in grasslands may be shrub canopies, many grasslands have been con- resilient to changes in insect fauna caused by verted to desert shrubland or juniper savanna human activities and even opportunistic of insects (Schlesinger et al. 1990; Loftin et al. 1995; associated with agricultural fields, irrigation MacPherson 1995). ditches, street lamps, and other man-made struc- Although some bat species (e.g., California tures, but such speculations should be demon- myotis) may benefit from the additional roosts strated, not assumed. provided by shrubs and other woody plants, the more significant impact on the local bat commu- nity may be the change of insect fauna from grass- RESEARCH IMPLICATIONS land species to desert shrubland or juniper sa- vanna species. Studies in Parmenter et al. (1994) An increasing number of land managers are suggested that grazing and other rangeland distur- concerned with conserving bats, protecting critical bances favor pest grasshopper species. Although bat habitat, and maintaining the role of bats in such changes may affect pallid bats that forage on ecosystem processes. Perception of bats by the such large terrestrial prey, the type of influence is public is improving as conservation educators unknown and depends on the degree of species- focus on the value of bats and dispel myths and specificity in the pallid bat’s diet, the availability of negative images. Most importantly, more scientists alternative prey, differences in prey behavior, are reducing the deficit of information on the life nutritional value, predator defenses, and other history, habitat requirements, community struc- factors. The effects of fire on various arthropod ture, and roles of bats in ecosystems. Much of what species are reviewed in Warren et al. (1987). How- is known about bats originates from research ever, fire suppression, not prescribed fire, is the focused on bats in forested environments, caves, more prevalent management activity today and and manmade structures. The lack of information the consequence of historic management practices. on grassland-dwelling bats and the potential Considering that more than 1200 insect species effects of management activities is apparent from from 11 orders feed on grasses in Arizona, New this review. Information from studies examining Mexico, Utah, Nevada, and Colorado (Warren et the resource requirements of grassland-dwelling al. 1987), there is an insufficient number of studies bats may subsequently be used to predict the to provide a comprehensive overview of the effects potential effects of human activities on bats or to of grazing and fire suppression on arthropod design studies that measure actual effects. Recom- community composition, structure, and distribu- mendations for future research include: tion. In addition, too little is known about diet and • Develop a comprehensive understanding of prey selection by grassland-dwelling bats to composition, distribution, and abundance of predict their responses to changes in the arthropod bats in grasslands. Conduct mist net, acousti- community. Knowledge of these factors would be cal, and cave and mine surveys at previously useful for interpreting the effects of agriculture, unsurveyed sites to provide a thorough including the cultivation of monoculture crops and coverage of grassland habitats. the application of pesticides, on the prey base of bats. • Determine what landscape features are used The diversity of arthropod orders found in by bats in grasslands and for what purposes. guano of any one bat species suggests a degree of Use radiotelemetry and light tagging to dietary plasticity in bats. However, differences in observe bat behavior, follow movements, and size, flight style, and echolocating ability may identify day and night roost sites. Knowledge restrict each bat species to a certain prey size range of which features are used by bats and sea- (Ross 1967). Perhaps as long as certain prey com- sons of use will allow planning of activities to munity characteristics (e.g., insect size distribution, minimize impacts on local bat populations.

60 • Identify food habits of grassland bats so that Armstrong, D. M.; Adams, R.A.; Freeman, J. 1994. dietary flexibility may be determined and the Distribution and ecology of bats of Colorado. effects of management activities may be Natural history inventory of Colorado No. 15. predicted. Determine foraging areas, food University of Colorado Museum, Boulder, CO. availability, and diet preference by radiote- Barclay, R.M.R.; Cash, K.J. 1985. A non-commensal lemetry, arthropod sampling, and fecal analy- maternity roost of the little brown bat (Myotis ses, respectively. Basic studies of the effects of lucifugus). Journal of Mammalogy. 66: 782-783. grazing, fire, etc. on arthropod communities Bee, J.W.; Glass, G.E.; Hoffmann, R.S.; Patterson, are also necessary. R.R. 1981. Mammals in Kansas. University of Kansas, Lawrence, KS. • Examine effects of human activities on bat Belwood, J.J.; Waugh, R.J. 1991. Bats and Mines: communities. Compare bat species composi- abandoned does not always mean empty. Ab- tion, abundance, and behavior before and stract. Bat Research News. 32: 66. after implementation of activities (prescribed Black, H.L. 1974. A north temperate bat commu- fire, new grazing regime, etc.), or between nity: structure and prey populations. Journal of treated and untreated sites. Mammalogy. 55: 138-157. • Determine if availability and diversity of Bock, C.E.; Bock, J.H.; Kenney, W.R.; Hawthorne, V.M. 1984. Responses of birds, rodents, and water, roost, or food resources influence bat vegetation to livestock exclosure in a semidesert species diversity and abundance. Examine grassland site. Journal of Range Management. such correlations by coupling bat surveys 37: 239-242. with evaluations of resource availability and Bogan, M. A. In press. California myotis. Myotis diversity in the surrounding area. Studies that californicus. In: D. E. Wilson (ed.). Mammals of manipulate water availability and monitor bat North America. Smithsonian Institution Press, activity may also determine the effect of water Washington, D. C. availability on use of grasslands by bats in the Branson, F.A. 1985. Vegetation changes on western arid Southwest. rangelands. Range Monograph No. 2. Society for • Investigate winter behavior and roost habits. Range Management, Denver, CO. Determine whether grassland bats migrate to Caire, W.; Smith, J.F.; McGuire, S.; Royce, M.A. hibernacula or remain locally. If bats remain 1984. Early foraging behavior of insectivorous local, identify structures used as hibernacula bats in western Oklahoma. Journal of Mammal- and develop recommendations for mainte- ogy. 65:319-324. nance and protection of these structures. Dick-Peddie, W.A. 1993. New Mexico Vegetation: Past, Present, and Future. University of New Our ability to understand bat ecology and Mexico Press, Albuquerque, NM. 244 pp. management in grassland and other ecosystems Fitch, J.H.; Shump, K.A.; Shump, A.U. 1981. Myotis increases as study techniques, technology, and velifer. Mammalian Species. 149: 1-5. interest by the research community develop. Using Findley, J.S.; Harris, A.H.; Wilson, D.E.; C. Jones. this information, managers may make more effec- 1975. Mammals of New Mexico. University of tive decisions regarding bat habitat, and educators New Mexico Press, Albuquerque, NM. may increase interest and appreciation for bats, Geluso, K.N. 1978. Urine concentrating ability and their unique ecology and behavior, and their role renal structure of insectivorous bats. Journal of in ecosystem function. Mammalogy. 59: 312-323. Genter, D.L. 1986. Wintering bats of the upper snake river plain: occurrence in lava-tube caves. LITERATURE CITED Great Basin Naturalist. 46: 241-244. Grant, W.E.; Birney, E.C.; French, N.R.; Swift, D.M. Altenbach, J.S.; Milford H.E. 1991. A program to 1982. Structure and productivity of grassland evaluate bat use and occupancy of abandoned small mammal communities related to grazing- mines in New Mexico. Abstract. Bat Research induced changes in vegetative cover. Journal of News. 32: 63. Mammalogy. 63: 248-260.

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